You've got to stop at the Natural Bridges safari park. It sounds like the tackiest place in the world but it's a riot and the kids will love it.

http://www.virginiasafaripark.com/

Speaking of kitchy in the area of Natural Bridge, Virginia, how about a stop at Dinosaur Kingdom where the dinosaurs attack Union soldiers? Ya gotta love it!
http://www.roadsideamerica.com/story/10790

A less kitchy choice is Hull's Drive-in in Lexington, VA. When's the last time you were in a drive-in? Never? Anyway, it's fun and family friendly.

http://hullsdrivein.com/

Luray Caverns aren't far off 81 in VA. Jog up to Blueridge Pkwy/Skyline Dr for a while and stop and walk along the Appalachain Trail for a short way.

See potato chips being made (and sample them) at Route 11 Potato Chip factory outside of New Market, VA or
the Museum of Frontier Culture in Staunton, VA where various homes from old Europe have been set up. People in native dress and farm animals..

The museum also has old American farms.

www.frontiermuseum.org

www.rt11.com

http://www.springsfarm.com/SpringsFarm.com_peachstand.asp

I never fail to stop here for a milkshake!

If you decide to visit the Route 11 factory, go to their website for directions. Follow the one that has you exit I-81 at Mt. Jackson which will allow you to go through the Meems Bottom Covered Bridge. There is parking and picnic tables at the east side of the bridge, and if your trip is in the summer, the kids can splash in the Shenandoah River. (It's very shallow there.)